Inside a stripper, a gas-solid separation process in a fluidized bed is basically a mass transfer process between a gaseous stripping fluid flowand a fluidized bed of solid particles.
In the petroleum refining, the purpose of the catalyst stripper of fluid catalytic cracking unit—FCCU is to remove the hydrocarbons adsorbed on the catalyst (spent catalyst) during the cracking reaction, before the regeneration stage.
The efficiency of the catalyst stripper has a significant impact on the overall profitability of an FCCU. Poor stripping reduces the efficiency of the process beyond causing higher temperatures in the regeneration stage, increasing the deactivation of the catalyst and the mechanical wear out on the processing unit.
The stripper performance is a function of several operational and design parameters.
In order to improve the contact between the stripping fluid and the spent catalyst and to enhance the efficiency of the gas-solid separation, an FCCU stripper contains internals. In this way, the use of strippers depends intrinsically on the proper selection of internals. The most commonly used are known as baffle-plates.
The petitioner's patent application PI 0403239 (U.S. application Ser. No. 10/643,968 filed Aug. 20, 2003), fully incorporated herein by reference, teaches a stripping apparatus in the spatial arrangement of the segmented baffles, parallel, arranged in sequence, the segment number as well as the plate thickness being dimensioned so as to reduce the coalescence of the bubble size of the stripping fluid as well as an homogeneous fluid dynamic distribution of the catalyst flux turbulence throughout the stripping vessel being secured. However, the geometry of the segmented baffle-plates, as proposed, does not eliminate the central stagnation zones, which results in a reduced stripping volume. Besides, the straight rips generate points of stress and allow the plates to become less resistant to erosion. Also, the segmentation does not allow for manufacturing baffle-plates in sizes suitable for industrial application.
Thus, the disadvantages of the technique are outweighed by this invention, described below, as regards a stripping apparatus for gas-solid separation process in a fluidized bed that maximizes the stripping volume and reduces erosion of the perforated baffle-plates of a stripper inside a separator vessel in an FCCU.